And on the claim in that tweet, I will repeat what I said on that thread:
"The most important thing to remember about chromosomes is this:
Chromosomes are not sex. They are not the definition of sex - neither in law nor biology. They are merely a mechanism which drives sex development. The starting point to be precise. [...]
In millions of years as humanoids on this planet and over 200,000 years as a species, we have not needed to look at chromosomes to know who is male and who is female. We still do not need it now. Because if we identify someone as male or female, we do so with better than 99% accuracy.
Sex is a description of a reproductive mechanism. This mechanism involves chromosomes at the start, then the SRY gene, then hormones which lead to the development of genitals along a predictable path, which then in turn produce hormones at puberty driving further development. Even abnormalities are predictable - we know what happens if any step of this mechanism fails.
That's why the definition of sex looks at the combination of chromosomes, gonads and genitalia. (This is how sex is also defined in law and why it is defined like that.)
That's also why different species whose chromosomal mechanisms differ from that of humans still have males and females. Because sex is a reproductive category - has your body developed the anatomy that typically produces large or small gametes?
You've got the anatomy for the production of large gametes? Congratulations, you're female.
You've got the anatomy for the production of small gametes? Congratulations, you're male.
How you get here is largely irrelevant. Wether your anatomy performs as expected is also irrelevant in deciding whether you are male or female.
And don't let these constant insinuations that our chromosomes might not be what we expect fool you. As Dr Emma Hilton (FondOfBeetles) reports from her own research looking at newborns and whether their sex chromosomes are not in line with with their sex - this is incredibly rare. 0.00017% kind of rare.
So if you know you're female, there's a 99.9983% chance you don't have a Y chromosome."
As for the person who tweeted this, it's incredibly unlikely that De Chapelle Syndrome goes undiagnosed until you're middle aged (this person is almost 50). This person has previously made a number of other claims, such as having Dissociative Identity Disorder, and such like. So this may be a cry for attention from someone who appears to be experiencing mental health issues.